1. Field of the Invention
The present invention relates generally to circuit interrupters and, more particularly, to a support structure for a circuit breaker latch. The invention also relates to a circuit breaker employing a support structure for a latch.
2. Background Information
Circuit interrupters, such as circuit breakers, are employed in diverse capacities in power distribution systems. A circuit breaker may include, for example, a line conductor, a load conductor, a fixed contact and a movable contact, with the movable contact being movable into and out of electrically conductive engagement with the fixed contact to switch the circuit breaker between an on or closed position and an off or open position, or between the on or closed position and a tripped or tripped off position. The fixed contact is electrically conductively engaged with one of the line and load conductors, and the movable contact is electrically conductively engaged with the other of the line and load conductors.
Circuit breakers may also include an operating mechanism having a movable contact arm upon which the movable contact is disposed, a pair of links, a main spring, a latch mechanism, a cradle and a movable operating handle that extends outside of a housing for the circuit breaker. The cradle is pivotally disposed between the latch mechanism and the links. One portion of the cradle pivots with respect to the housing while another portion of the cradle has a latch ledge, which is latched by the latch mechanism.
It is known to employ latch mechanisms including a primary latch and a secondary latch. An accurate, consistent position of the primary latch over the life of the circuit breaker is essential for good performance. As there is relative motion between the primary latch and its support structure, low wear and low friction are desirable for the interface between the primary latch and the support structure. The primary latch is often a flat metal stamping. To minimize space requirements, it is desirable to connect the primary latch directly to the support structure (e.g., side plates, such as flat stampings) in a manner that allows relative motion of the primary latch relative to the support structure. It is impractical to harden the side plates in just the area where the primary latch attaches, although such latch can be hardened.
There is room for improvement in support structures for circuit interrupter latches and in circuit breakers employing such support structures.